The invention relates to a liquid agitation apparatus, and more particularly, to such apparatus which is intended to be used in an automatic agitation of a reaction solution comprising a mixture of a liquid to be examined and a reagent.
To determine the quantity of a substance such as an enzyme contained in a blood sample by means of a chemical analyzer, a coenzyme is mixed with the liquid sample and the absorbance of the coenzyme determined. With this determining technique, there exists a proportional relationship between the absorbance and the time, a change in the absorbance indicating the quantity of the enzyme. It is known that the quantity of the enzyme is a function of temperature. Consequently, in order to assure reliable data, it is essential that the liquid to be examined, such as blood, be uniformly mixed with the reagent and that the mixed reaction solution be maintained at a constant temperature during the determination process.
A conventional apparatus used to make such a determination will be described with reference to FIG. 1. A thermostat block 1 is kept at a constant temperature in an automatic manner by using the combination of a heating element and a temperature sensor. It includes a preheater assembly 1a and a measuring cell 1b. The preheater assembly 1a is formed with a plurality of openings 3 which receive removable reaction vessels 2 in the form of transparent, hollow square pillars which contain a reaction solution. The measuring cell 1b includes an opening 4 which is adapted to receive a reaction vessel 2 containing the reaction solution, and an opening 5 which is formed to extend through the opening 4 for the purpose of obtaining photometric data. A light source 6, which may comprise a tungsten lamp, emits a photometric flux of radiation passing substantially through the center of one side 2a of the vessel 2 which is exposed through the opening 5. A photoelectric transducer element 7, which may comprise a silicon blue cell, is disposed on the opposite side of the cell from the lamp to receive light passing through the cell.
In using the conventional apparatus illustrated in FIG. 1, a plurality of reaction vessels 2 containing a reagent are loaded in the openings 3 for the purpose of preheating. When a given temperature is reached, one of the vessels 2 is removed, a specimen is added thereto and is shaken by hand or by using a stirring rod, and the vessel 2 is loaded in the opening 4. A flux of radiation P having a given optical wavelength is emitted by the source 6, passes through the opening 5 and through the reaction solution contained in the vessel 2 disposed in the opening 4, and finally received by the transducer element 7. The element 7 produces an electrical signal in accordance with the magnitude of the transmitted portion of the radiation flux P and applies the signal to an arithmetic circuit, which calculates the absorbance of the reaction solution.
In the arrangement described above, the apparatus is not provided with stirring means in itself and hence the vessel 2 must be shaken by hand or stirred by some other means after it is removed from opening 3. This represents both an operational inconvenience and a cause of error in the measurement in that the vessel 2 is removed from the apparatus and a stirring rod, which may be at a different temperature, is brought into contact with the reaction solution, thus causing a rapid drop in the temperature of the preheated solution. Also, the period of agitation varies from vessel to vessel, so that the agitation of the solution may be insufficient.